A comparative study of two different doses of dexmedetomidine on haemodynamic responses to induction of anaesthesia and tracheal intubation

Tracheal intubation and direct laryngoscopy are considered as the most critical event during administration of general anaesthesia. Dexmedetomidine is an alfa-2 adrenergic agonist use for control of haemodynamic response to laryngoscopy and tracheal intubation. Our study consisted 60 patients of ASA grade I or II, scheduled for elective gynaecological, general and ENT surgery, divided into two groups of 30 patients each. Group A received injection dexmedetomidine 1.0 μg.kg over 10 minutes and Group B received injection dexmedetomidine 0.5 μg.kg over 5 min, both diluted in 10 ml normal saline. One min after dexmedetomidine, injection thiopental sodium 5 mg.kg -1 and injection vecuronium bromide 0.1 mg.kg -1 were administered intravenously for induction. Intubation was performed after 3 min. The parameters like heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) and O2 saturation (SpO2) were recorded at pre-induction, 60 seconds (sec) after dexmedetomidine (t1), 60 sec after induction (t2), during laryngoscopy and tracheal intubation (t3), 1 min after intubation (t4), 2 min after intubation (t5) and 5 min after intubation (t6). Data obtained was analysed using unpaired t-test. We have observed statistically highly significant (p<0.01) increase in mean SBP, DBP and MAP in Group B as compare to Group A at t3 and t4 while at pre-induction, t1, t2, t5 and t6, mean SBP, DBP and MAP were comparable in both groups (p>0.05). There were statistically highly significant (p<0.01) increases in mean HR in Group B as compare to Group A at t3, t4, t5 and t6 while it was comparable (p>0.05) at pre-induction, t1 and t2 in both groups. There was no significant changes in SpO2 in both groups at all intervals (p>0.05). We conclude that dexmedetomidine 1 μg.kg is more effective than 0.5 μg.kg in attenuating haemodynamic responses to laryngoscopy and tracheal intubation, without any systemic side effects.